Electrical circuitry often must be protected from disruptions caused by electromagnetic intereference (EMI) and radio frequency interference (RFI) entering the system.
In addition to protecting electronic equipment against EMI/RFI energy, there is also a need to protect the equipment against power surges owing to electrostatic discharges (ESD) and electromagnetic pulse (EMP). The high voltage generated by ESD and EMP can damage voltage sensitive integrated circuits and the like.
Frequently today's electronic circuitry requires the use of high density, multiple contact electrical connectors. There are many applications in which it is desirable to provide a connector with a filtering capability, for example, to suppress EMI and RFI. To retain the convenience and flexibility of the connector, however, it is desirable that the filtering capability be incorporated into connectors in a manner that will permit full interchangability between the connectors and their unfiltered counterparts. In particular, any filter connector should also in many instances retain substantially the same dimensions as the unfiltered version and should have the same contact arrangement so that either can be connected to an appropriate mating connector. Additionally it is sometimes desirable to filter only certain lines within a connector and to use the same basic connector in a number of applications, each requiring different selected lines to be filtered.
One means to protect against undesirable interference without altering the internal structure of a connector is by the use of shielding. The shielding may take several forms. For adequate protection, it is essential, however, that there be no break in continuity of the shielding.
Other means for protecting against interference include the use of internal filtering schemes which include the use of filter sleeves and planar filter members. Both of these methods generally require the additional space within the connector to accommodate the sleeves or other filtering devices. Furthermore, connectors of this type often include a number of labor intensive steps during the manufacture of the connectors. These connectors are not readily manufacturable by automatic equipment.
In many instances it is desirable to have an external filtering device that is an "add-on" device to provide filtering to an already existing non-filtered connector. This is particularly desirable in instances when the same basic connector may be used in a number of different applications, each requiring filtering of different lines in the connector. It is also desirable that method be found to that will lend itself to automation of the assembly line by robotic devices and the like that will enable filtered connectors to be manufactured on a more cost effective manner.